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.\" $Id: form_driver.3x,v 1.33 2020/02/02 23:34:34 tom Exp $
.TH form_driver 3X ""
.de bP
.ie n  .IP \(bu 4
.el    .IP \(bu 2
..
.SH NAME
\fBform_driver\fR,
\fBform_driver_w\fR \- command-processing loop of the form system
.SH SYNOPSIS
\fB#include <form.h>\fR
.br
\fBint form_driver(FORM *\fP\fIform\fP\fB, int \fP\fIc\fP\fB);\fP
.br
\fBint form_driver_w(FORM *\fP\fIform\fP\fB, int \fP\fIc\fP\fB, wchar_t \fP\fIwch\fP\fB);\fP
.br
.SH DESCRIPTION
.SS form_driver
Once a form has been posted (displayed), you should funnel input events to it
through \fBform_driver\fR.  This routine has three major input cases:
.bP
The input is a form navigation request.
Navigation request codes are constants defined in \fB<form.h>\fP,
which are distinct from the key- and character codes returned
by \fBwgetch\fP(3X).
.bP
The input is a printable character.
Printable characters (which must be positive, less than 256) are
checked according to the program's locale settings.
.bP
The input is the KEY_MOUSE special key associated with an mouse event.
.SS form_driver_w
.PP
This extension simplifies the use of the forms library using wide characters.
The input is either a key code (a request) or a wide character
returned by \fBget_wch\fP(3X).
The type must be passed as well,
to enable the library to determine whether the parameter
is a wide character or a request.
.SS Form-driver requests
.PP
The form driver requests are as follows:
.TS
l l
_ _
l l.
\fIName\fR	\fIDescription\fR
REQ_BEG_FIELD	Move to the beginning of the field.
REQ_BEG_LINE	Move to the beginning of the line.
REQ_CLR_EOF	Clear to end of field from cursor.
REQ_CLR_EOL	Clear to end of line from cursor.
REQ_CLR_FIELD	Clear the entire field.
REQ_DEL_CHAR	Delete character at the cursor.
REQ_DEL_LINE	Delete line at the cursor.
REQ_DEL_PREV	Delete character before the cursor.
REQ_DEL_WORD	Delete blank-delimited word at the cursor.
REQ_DOWN_CHAR	Move down in the field.
REQ_DOWN_FIELD	Move down to a field.
REQ_END_FIELD	Move to the end of the field.
REQ_END_LINE	Move to the end of the line.
REQ_FIRST_FIELD	Move to the first field.
REQ_FIRST_PAGE	Move to the first page.
REQ_INS_CHAR	Insert a blank at the cursor.
REQ_INS_LINE	Insert a blank line at the cursor.
REQ_INS_MODE	Enter insert mode.
REQ_LAST_FIELD	Move to the last field.
REQ_LAST_PAGE	Move to the last field.
REQ_LEFT_CHAR	Move left in the field.
REQ_LEFT_FIELD	Move left to a field.
REQ_NEW_LINE	Insert or overlay a new line.
REQ_NEXT_CHAR	Move to the next char.
REQ_NEXT_CHOICE	Display next field choice.
REQ_NEXT_FIELD	Move to the next field.
REQ_NEXT_LINE	Move to the next line.
REQ_NEXT_PAGE	Move to the next page.
REQ_NEXT_PAGE	Move to the next page.
REQ_NEXT_WORD	Move to the next word.
REQ_OVL_MODE	Enter overlay mode.
REQ_PREV_CHAR	Move to the previous char.
REQ_PREV_CHOICE	Display previous field choice.
REQ_PREV_FIELD	Move to the previous field.
REQ_PREV_LINE	Move to the previous line.
REQ_PREV_PAGE	Move to the previous page.
REQ_PREV_WORD	Move to the previous word.
REQ_RIGHT_CHAR	Move right in the field.
REQ_RIGHT_FIELD	Move right to a field.
REQ_SCR_BCHAR	Scroll the field backward a character.
REQ_SCR_BHPAGE	Scroll the field backward half a page.
REQ_SCR_BLINE	Scroll the field backward a line.
REQ_SCR_BPAGE	Scroll the field backward a page.
REQ_SCR_FCHAR	Scroll the field forward a character.
REQ_SCR_FHPAGE	Scroll the field forward half a page.
REQ_SCR_FLINE	Scroll the field forward a line.
REQ_SCR_FPAGE	Scroll the field forward a page.
REQ_SCR_HBHALF	Horizontal scroll the field backward half a line.
REQ_SCR_HBLINE	Horizontal scroll the field backward a line.
REQ_SCR_HFHALF	Horizontal scroll the field forward half a line.
REQ_SCR_HFLINE	Horizontal scroll the field forward a line.
REQ_SFIRST_FIELD	Move to the sorted first field.
REQ_SLAST_FIELD	Move to the sorted last field.
REQ_SNEXT_FIELD	Move to the sorted next field.
REQ_SPREV_FIELD	Move to the sorted previous field.
REQ_UP_CHAR	Move up in the field.
REQ_UP_FIELD	Move up to a field.
REQ_VALIDATION	Validate field.
.TE
.PP
If the second argument is a printable character, the driver places it
in the current position in the current field.
If it is one of the forms
requests listed above, that request is executed.
.SS Field validation
The form library makes updates to the window associated
with form fields rather than directly to the field buffers.
.PP
The form driver provides low-level control over updates to the form fields.
The form driver also provides for validating modified fields
to ensure that the contents
meet whatever constraints an application may attach using \fBset_field_type\fP.
.PP
.PP
You can validate a field without making any changes to it using
\fBREQ_VALIDATION\fP.
The form driver also validates a field in these cases:
.bP
a call to \fBset_current_field\fP attempts to move to a different field.
.bP
a call to \fBset_current_page\fP attempts to move
to a different page of the form.
.bP
a request attempts to move to a different field.
.bP
a request attempts to move to a different page of the form.
.PP
In each case, the move fails if the field is invalid.
.PP
If the modified field is valid, the form driver copies the modified
data from the window associated with the field
to the field buffer.
.SS Mouse handling
.PP
If the second argument is the KEY_MOUSE special key, the associated
mouse event is translated into one of the above pre-defined requests.
Currently only clicks in the user window (e.g., inside the form display
area or the decoration window) are handled.
.PP
If you click above the display region of the form:
.RS 3
.TP
a REQ_PREV_FIELD is generated for a single click,
.TP
a REQ_PREV_PAGE is generated for a double-click and
.TP
a REQ_FIRST_FIELD is generated for a triple-click.
.RE
.PP
If you click below the display region of the form:
.RS 3
.TP
a REQ_NEXT_FIELD is generated for a single click,
.TP
a REQ_NEXT_PAGE is generated for a double-click and
.TP
a REQ_LAST_FIELD is generated for a triple-click.
.RE
.PP
If you click at an field inside the display area of the form:
.RS 3
.bP
the form cursor is positioned to that field.
.bP
If you double-click a field,
the form cursor is positioned to that field
and \fBE_UNKNOWN_COMMAND\fR is returned.
This return value makes sense,
because a double click usually means that an field-specific action should
be returned.
It is exactly the purpose of this return value to signal that an
application specific command should be executed.
.bP
If a translation
into a request was done, \fBform_driver\fR returns the result of this request.
.RE
.PP
If you clicked outside the user window
or the mouse event could not be translated
into a form request an \fBE_REQUEST_DENIED\fR is returned.
.SS Application-defined commands
.PP
If the second argument is neither printable nor one of the above
pre-defined form requests, the driver assumes it is an application-specific
command and returns \fBE_UNKNOWN_COMMAND\fR.  Application-defined commands
should be defined relative to \fBMAX_COMMAND\fR, the maximum value of these
pre-defined requests.
.SH RETURN VALUE
\fBform_driver\fR returns one of the following error codes:
.TP 5
.B E_OK
The routine succeeded.
.TP 5
.B E_BAD_ARGUMENT
Routine detected an incorrect or out-of-range argument.
.TP 5
.B E_BAD_STATE
Routine was called from an initialization or termination function.
.TP 5
.B E_NOT_POSTED
The form has not been posted.
.TP 5
.B E_INVALID_FIELD
Contents of field is invalid.
.TP 5
.B E_NOT_CONNECTED
No fields are connected to the form.
.TP 5
.B E_REQUEST_DENIED
The form driver could not process the request.
.TP 5
.B E_SYSTEM_ERROR
System error occurred (see \fBerrno\fR(3)).
.TP 5
.B E_UNKNOWN_COMMAND
The form driver code saw an unknown request code.
.
.SH SEE ALSO
\fBcurses\fR(3X),
\fBform\fR(3X),
\fBform_field_buffer\fR(3X),
\fBform_field_validation\fR(3X),
\fBform_fieldtype\fR(3X),
\fBform_variables\fR(3X),
\fBgetch\fR(3X).
.SH NOTES
The header file \fB<form.h>\fR automatically includes the header files
\fB<curses.h>\fR.
.SH PORTABILITY
These routines emulate the System V forms library.
They were not supported on
Version 7 or BSD versions.
.SH AUTHORS
Juergen Pfeifer.
Manual pages and adaptation for new curses by Eric S. Raymond.
